The main aim of this research project both in the current year (10/1/72 to 9/30/73) and the next year (10/1/73 to 9/30/74) is the study of the electronic structure and properties of heme derivatives and the changes that occur on attachment to the protein chain. In the biochemical function of hemoglobin namely the transport of oxygen at least three questions need to be answered. These are: the electronic structure aspects of the attachment of oxygen or other molecules to the iron atom, the mechanism of conformational changes accompanying oxygenation and the question of cooperativity among various chains in hemoglobin with respect to oxygenation.